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Core components of new energy vehicles—understanding electronically controlled IGBT modules from scratch
Date: Mar 20,2024 Views: 163
Core components of new energy vehicles—understanding electronically controlled IGBT modules from scratchIGBT
The current module system of new energy vehicles consists of many parts, such as batteries, VCU, BSM, motors, etc., but these are relatively mature products. Domestic and foreign module manufacturers have developed many, but there is one module that needs to attract industry attention. The internal emphasis is on the motor drive part, which is the core component of the motor drive part, IGBT (Insulated Gate Bipolar Transistor Insulated Gate Bipolar Transistor Chip).
If you want to learn about automotive electronic control IGBT modules from scratch, this article is enough!
According to data from the Passenger Car Association, the domestic retail penetration rate of new energy vehicles in June 2022 was 27.4%. On June 29, 2022, the European Union announced that the 27 EU member states had initially reached an agreement that Europe would ban the sale of fuel vehicles in 2035. . The market is becoming more and more prosperous, and at the same time, newly released new energy models in China are also blooming. Whether they are ordinary consumers, relevant practitioners in the new energy vehicle industry, or investors in the primary and secondary markets, they are gradually paying close attention to some core components of new energy vehicles, especially the power device IGBT module. Today, the editor will use the form of a question and answer Let me explain it to you, hoping to help you with a more simple explanation.
The role of electric drive system and IGBT module
To understand the IGBT module, we must first understand the electric drive system of new energy vehicles. First, summarize how the electric drive system works in one sentence: When driving a new energy vehicle, the motor controller converts the direct current (DC) released by the power battery into Alternating current (AC) (this process is called inversion) makes the drive motor work. The motor converts electrical energy into mechanical energy, and then through the transmission system (mainly the reducer) to make the wheels of the car run. In turn, the process of converting and storing the mechanical energy of the wheels into the battery is kinetic energy recovery.
What are "three-electric system" and "electric drive system"?
The three electric systems, namely the power battery (referred to as battery), the drive motor (referred to as motor), and the motor controller (referred to as electronic control), are also regarded as the three major components, which together account for more than 70% of the total cost of new energy vehicles. It is the component that determines the core sports performance of the entire vehicle.
For electric drive systems, we generally simply refer to the motor, electronic control, and reducer as the electric drive system.
But strictly speaking, according to the prospectus of Jinjing Electric, the electric drive system includes three major assemblies: the drive motor assembly (which converts the electrical energy of the power battery into rotating mechanical energy and is the source of output power), and the controller assembly ( Based on the hardware and software design of power semiconductors, the working status of the drive motor is controlled in real time, and other control functions are continuously enriched), the transmission assembly (the output speed is reduced and the output torque is increased through the gear set to ensure that the electric drive system continues to operate at high efficiency interval).
What is an “all-in-one electric drive system”?
At first, the motor, electronic control, and reducer were all independent components, but with the advancement of technology, we brought these three parts together into one component, which became a "three-in-one electric drive." The purpose of integration is mainly to save space, reduce weight, improve performance, and reduce costs.
Currently on the market, BYD's Fudi Power's "eight-in-one electric powertrain" with a high degree of integration is the most highly integrated. This eight-in-one electric drive system integrates a drive motor, motor controller, reducer, on-board charger, and DC powertrain. Converter, distribution box, vehicle controller, battery manager.
Of course, this does not mean that the higher the integration level, the better. Issues such as heat dissipation structure design, system stability, and production process maturity need to be addressed. For consumers, later maintenance costs are also a big problem. Therefore, the specific method of selecting an all-in-one electric drive system needs to be comprehensively analyzed.
How exactly do IGBT modules work?
Among the electronic control modules, the IGBT module is the core component of the inverter. To summarize its working principle:
Through the non-on and off semiconductor characteristics, without considering the transition process and parasitic effects, we regard a single IGBT chip as an ideal switch. We build a parallel and series structure of several IGBT chip units inside the module. When DC power passes through the module, the outflow direction and frequency of the current are changed through the rapid opening and closing of different switch combinations, thereby outputting the AC power we want.
IGBT module structure and automotive IGBT module applications
The role of the IGBT module in the electric drive system has been mentioned above. Let’s take a closer look at the structure of the IGBT module.
What does the actual IGBT module look like?
The standard packaging form of the IGBT module is a flat rectangular parallelepiped. The picture below shows the top view of the HP1 module. The outermost white part is a plastic shell, and the bottom is a metal bottom plate (usually copper material) for heat conduction and heat dissipation. You can see that there are many terminals and pins outside the module, each with its own function:
1 is DC positive, 2 is DC negative; 3, 4, 5 are the U, V, W interfaces of the three-phase alternating current; 6, 25, 22 are the signal terminals of the collector, 7, 9, 11, 13, 15, 17 It is the gate signal terminal; 8, 10, 12, 14, 16, and 18 are the emitter signal terminals; 19 is the DC negative signal terminal; 23 and 24 are the NTC thermistor terminals.
As shown in the figure above, in the IGBT module/single tube, the first unit is generally called an IGBT single tube, the second unit is a single bridge arm (half bridge), the fourth unit is an H bridge (single-phase bridge), and the sixth unit is a three-phase bridge. (Full bridge), seven units are generally six units + one braking unit, and eight units are generally six units + braking unit + precharge unit.
A unit consists of 1 pair, 2 pairs or 3 pairs of FRD+IGBT. One pair can be 1 FRD+1 IGBT, or 1 FRD+2 IGBT, etc.
For the specific physical object, please refer to the picture below. This is a 6-unit IGBT module.
6. What is the production process of IGBT modules?
As shown in the figure above, you can see the cross-section interface of the IGBT module. The basic structures of the modules in the current shell sealing process are not much different. The process of IGBT module packaging is roughly as follows:
SMT → Vacuum reflow soldering → Ultrasonic cleaning →
For patching, first patch each die on the IGBT wafer to the DBC. DBC is a copper-clad ceramic substrate with ceramic in the middle and copper-clad on both sides. DBC is similar to PCB and plays the role of conductivity and electrical isolation. Commonly used ceramic insulating materials are aluminum oxide (Al2O3) and aluminum nitride (AlN);
Vacuum welding, after patching, the die and DBC are fixed by vacuum welding. Generally, the solder is tin sheet or solder paste;
X-ray void detection needs to detect bubbles, that is, voids, that appear during the connection process. The existence of voids will seriously affect the thermal resistance and heat dissipation efficiency of the device, leading to problems such as overheating, burnout, and explosion. Generally, automotive IGBT modules require a void rate of less than 1%;
Next is the wire bonding process, which uses metal wires to bond the die to the DBC. The most commonly used ones are aluminum wires. Other commonly used ones include copper wires, copper strips, and aluminum strips;
There will be a series of appearance inspections and static tests in the middle, and modules with problems in the process will be scrapped directly;
Repeat the above process to weld and bond the DBC to the copper base plate, followed by glue filling, encapsulation, laser coding and other processes;
Final functional testing will be done before leaving the factory, including dynamic testing of electrical performance, insulation testing, reverse bias testing, etc.
7. What are the common automotive IGBT module packaging types?
Econodual series half-bridge package is mainly used in commercial vehicles. The main specifications are 1200V/450A, 1200V/600A, etc.;
HP1 full-bridge package is mainly used in small and medium-power models, including some A-class cars and most A0 and A00 cars. The peak power is generally within 70kW. The main models are 650V400A. Other specifications include 750V300A, 750V400A, 750V550A, etc. ;
HPD full-bridge package, used in medium and high-power vehicles, most A-class vehicles and above, with 750V820A specifications occupying the mainstream market, and other specifications such as 750V550A;
DC6 full-bridge packaging, an integrated packaging solution based on UVW three-phase full-bridge, has the characteristics of compact packaging, high power density, and good heat dissipation performance;
TO247 single-tube parallel connection, there are also a small number of electronic control system solutions using TO247 single-tube packaging on the market. There are two main advantages of using a single-tube parallel connection solution: ① The single-tube solution can achieve flexible circuit design. Just use the corresponding single-tube parallel connection for the required current, so the cost also has certain advantages; ② The problem of parasitic inductance is better than that of IGBT The module is easy to solve. However, there are also some difficulties that need to be solved when using single tubes in parallel: ① It is difficult to share and balance the current between each paralleled single tube, and it is difficult to ensure consistency, such as achieving simultaneous opening and closing, the same current, temperature, etc.; ② The customer's system design and process are very difficult; ③ There are many interfaces and the requirements for the production line are very high.
8. What testing and verification are required for automotive IGBT modules?
The requirements for product performance and quality of automotive IGBT modules are significantly higher than those in the consumer and industrial control fields. Therefore, automotive certification has become the most important barrier to the automotive IGBT module market. Generally speaking, automotive grade IGBTs require a model introduction cycle of about 2 years. .
The testing standards for automotive IGBT modules mainly refer to AEC-Q101 and AQG-324. At the same time, car companies will put forward corresponding requirements based on the characteristics of their own models. The main testing methods include: parameter testing, ESD testing, insulation withstand voltage, mechanical vibration, mechanical impact, High temperature aging, low temperature aging, temperature cycle, temperature shock, UHAST (high temperature and high humidity unbiased), HTRB (high temperature reverse bias), HTGB (high temperature bias erased), H3TRB/HAST (high temperature and high humidity reverse bias), power cycle, Solderability.
Among them, power cycle and temperature cycle are representative durability tests, which have extremely strict requirements. For example, the number of power cycles may range from tens of thousands to one hundred thousand times. The main purpose is to test the durability of mechanical connection layers such as bonding wires and welding layers. The main failure mechanism during the test is that the thermal expansion coefficients of the chip, bonding wire, DBC, solder, etc. are inconsistent, resulting in bonding wire falling off and breaking, chip solder layer separation, and solder aging.
China's automotive IGBT market situation
With the rapid development of the domestic new energy vehicle industry, the upper reaches of the industry chain are gradually completing domestic substitution and even leading the world's trends, such as vehicle brands, power batteries, battery materials, etc., which are already relatively advanced. The automotive electronic control IGBT module is the core power device of new energy vehicles. It has been monopolized by foreign suppliers such as Infineon, ON Semiconductor, Semiconductor, and Mitsubishi Electric. However, with the development of BYD Semiconductor, Star Semiconductor, and The rise of domestic suppliers such as CRRC Times, Silan Micro, and Cuizhan Micro are currently able to meet domestic demand to a certain extent. I believe that domestic automotive semiconductor companies will be bigger and stronger in the near future!
